Electric field-responsive solid state devices

ABSTRACT

1,070,261. Semi-conductor devices. INTERNATIONAL BUSINESS MACHINES CORPORATION. May 26, 1964 [June 10, 1963], No. 21796/64. Heading H1K. The invention is based on the discovery that when an electric field in excess of 2000 volts/cm. is set up in a crystal of gallium arsenide, the current flow between a pair of electrodes on the body fluctuates at microwave frequency. In general the fluctuations are random noise but if the electrodes are at the ends of a body whose length L lies between 2 x 10&lt;SP&gt;-2&lt;/SP&gt; and 1 x 10&lt;SP&gt;-4&lt;/SP&gt; cm. and the field is set up by applying a suitable potential difference to these electrodes, the current fluctuations are coherent oscillations with a frequency, or set of harmonic frequencies, given by f = nv/L, where / is the frequency, n is an integer and v is the carrier drift velocity. The claims are directed to a device (which need not be made of gallium arsenide) exhibiting the above effect and to the use of the effect as a method of generating microwave oscillations. In the drawings (not shown). Figs. 1 and 2 depict the electrical characteristics of the device; Fig. 3 an oscillator circuit consisting solely of the device, a source of D.C. power and a load; and Fig. 4 a jig which is used to provide a suitably dimensioned Ga As wafer with tin electrodes. In this jig the wafer is located between two tin spheres which are subsequently melted and alloyed to the wafer, the end product (Fig. 5a, not shown) being a cylinder consisting of two tin rods with a disc of gallium arsenide between them. This is subsequently shaped by grinding to a triangular cross-section, embedded in epoxy resin, the resin partly removed to expose one rectangular face of the triangular prism and attached by that face to a suitable insulating block carrying phosphor bronze contacts to the tin electrodes. The steps of this process are depicted in Figs. 5b to 5f (not shown).

J. B. GUNN 3,

ELECTRIC FIELD-RESPONSIVE SOLID STATE DEVICES 9 Shecs-Sheet 1 Jan. 23,31.968

Filed June 12, 1964 INVENTOR JOHN B. GUNN B%% K ATTORNEY T U DI E M 0LIIJ m m 5 B L D w A 3 O L G ET F ID 4 4 1 V\ RE M J% L L U W 1 2 LI O 80 S W8 2 3 T WQCLU G 7 an, F T ,///M a E w/ O 7. w? M A G G Jan. 23,1968 J. B. GUNN 3,365,533

ELECTRIC FIELD-RESPONSIUE SOLID STATE DEVICES Filed June 12, 1964 9Sheets'-Shet 2 Jan. 23, 1968 J. B. GUNN 3,365,583

ELECTRIC FIELD-RESPONSIVE SOLID STATE DEVICES Filed June 12, 1964 FIGSFIG. 7A

FIGTB 9 Sheets-Sheet 3 T0 OSCILLOSCOPE M I CA INSULATION OHM IC CONTACTANODE GoAs p I I I NPUT PULSE (PARAMETER) INCREASING XI (PARAMETER)INCREASING Jan. 23, 1968 J. B. GUNN 3,365,583

ELECTRIC .FIELD-RESPONSIVE SOLID STATE DEVICES Filed June 12, 1964 9Sheets-Sheet 4 INCREASING TIME t (INTERVAL FiG.8

J. B. GUNN Jan 23, 1968 ELECTRIC FIELD-RESPONSIVE SOLID STATE DE 9Sheets-Sheet Filed June 12, 1964 Jan. 23, 1968 J. B. GUNN 3,365,583

ELECTRIC FIELD-RESPONSIVE] SOLID STATE DEVICES Filed June 12, 1964 9Sheets-Sheet 3 56.10 A -VT 52 FEGJHA .1. B. GUNN 3,365,583

ELECTRIC FIELD-RESPONSIVE SOLID STATE DEVICES Jan. 23, 1968 9Sheets-Sheet 7 Filed June 12, 1964 f \SOLDER AuGe CONTACT Jan. 23, 1968J. B. GUNN 3,365,583

ELECTRIC FIELD-RESPONSIVE SOLID STATE DEVICES Filed June 12, 1964 9Sheets-Sheet 8 FIG. 15A FBG.15

FiG.-16A

.1. B. GUNN 3,365,583

ELECTRIC FIELD-RESPONSIVE SOLID STATE DEVICES 9 Sheets-Sheet 'J Jan. 23,1968 Filed June 12, 1964 Q Q EH a9 9 .H. F S W A? 19: U T1 W WC [W S 0 Sw WTM m U P M P NW A 0.1 m m m T A mm X 9 m u ll BMW NG W m a W MU G T mL K 3 F Mmww n 2 M w OUTPUIS nite This invention relates to soliddevices and, more particularly, to a novel device whose operation isbased on the formation of electrical shock waves in crystallinematerials and, more specifically, in semiconductor crystalline bodies.

This application is a continuation-in-part of application Ser. No.286,700, now abandoned. The invention disclosed in the above-mentionedapplication, which was also assigned to the assignee of the presentinvention, was conceived in terms of a solid state microwave oscillator.However, it has been discovered that the basic underlying phenomenonwhich gives rise to the formation and amplification of microwaves asdescribed in the latter application can also be utilized in other modesand types of operations. Accordingly, a whole range or class of devicesis envisioned in view of the fundamental character of this underlyingphenomenon.

The observable effect which led to the development of the microwaveoscillator described in application Ser. No. 286,709 was the instabilitydiscovered in certain semiconductor crystals, notably of GaAs and InP,when subjected to high electric fields above a certain threshold involts/ cm. When a uniform electric field of such high value is appliedto a crystal specimen, the aforesaid instability is observed as afluctuation of the current flowing when a constant voltage is appliedbetween two ohmic contacts attached to the crystal. A time dependentdecrease in the current is observed under these conditions; thisdecrease, which in long specimens resembles random noise, is in shortSpecimens found to be periodic and of an extremely high frequencydetermined by the specimen length.

It has since been discovered that the aforesaid current instability isassociated with the occurrence of moving regions of very high electricfield (shock waves) which propagate with a velocity of the order of 10cm./sec. Hence, the previously observed microwave oscillations are but asingle peculiar manifestion of the underlying phenomenon of electricalshock waves whose movement, in this particular case, happens to becyclical in nature through the specimen, that is, they move from one end(the cathode) to the other end (the anode) and they repeat this movementover and over again.

A fundamental object of the present invention is to provide devicesutilizing electrical shock waves in their various manifestations incrystalline bodies.

Another basic object is to exploit the extremely high speed phenomenonof the electrical shock waves present in crystalline bodies to performlogical functions in a distributed structure.

A specific object of the present invention is to permit the generationof microwave power.

Another object of the present invention is to enable the generation ofmicrowave power at frequencies above 100 megacycles.

A further object of the present invention is to provide a microwaveoscillator which develops frequencies on the order of 500 to 6500megacycles.

An additionel object of the present invention is to provide a microwaveoscillator whose operation is dependent upon high electric field effectswhich occur in semiconductors.

States Patent Another object of the present invention is to producemicrowave oscillations in a device which is characterized by a verysimple structure.

A more specific object is to obtain microwave oscillations abovemegacycles in a device comprising small element or wafer ofsemiconductor material to which only ohmic contacts need be made.

A further object is to provide microwave oscillations which aresubstantially independent of external circuit means.

Another object is to provide a microwave oscillator device having onlytwo terminals.

Another object is to provide a simple oscillating device which is notdependent on the manifestation of negative resistance in its VIcharacteristic.

Another object is to provide a microwave oscillator which can be rapidlyand very simply modulated.

A further object is to provide amplification by the utilization ofelectrical shock waves produced in a crystalline body.

Additional objects are to provide applications for the aforesaidelectrical shock wave phenomenon to perform the functions of amplifying,pulse forming, stretching, and delaying and, also, logical functions ofvarious types, for example, AND, INCLUSIVE, OR, NOR, INHIBIT, etc.

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings.

In the drawings:

FIGURE 1 is a plot of the current vs. electric field illustrative of thebasic phenomenon of the present invention.

FIGURES 2A and 2B are diagrams of current pulse shapes obtainable due tothe phenomenon of the present invention.

FIGURE 3 is a simple schematic illustration of the basic device of thepresent invention connected in circuit to provide microwaveoscillations.

FIGURE 4 is a cross-sectional view illustrating the technique ofapplying contacts to the semiconductor sample.

FIGURES 5A through 5F are views of the device of the present inventionbeing packaged for use in a circuit.

FIGURE 6 is a schematic diagram of a semiconductor sample and apparatusfor measuring its parameters.

FIGURES 7A and 7B are graphs wherein voltage is plotted against time andwith distance X along the sample as parameter.

FIGURE 8 is a graph wherein dV(X,t) /dt is plotted against the distanceX.

FIGURES 9A and 9B are diagrams wherein the data of FIGURES 7A, 7B, and 8are represented by a time dependent potential distribution.

FIGURES 10A and 10B are pulse diagrams illustrating the voltage appliedto the semiconductor body and the resultant current through thesemiconductor body, respectively.

FIGURES 11A, 11B, and 11C are schematic diagrams illustrating severalschemes for the imposition of local high fields.

FIGURES l2 and 13 are output pulse diagrams for various voltage waveforms applied to the device of FIG- URES 11A, 11B, and 11C.

FIGURE 14 is a perspective view of a typical semiconductor body shownconnected to a header for installation in a. circuit.

FIGURES 15A and 15B are schematic diagrams illustrating other ways ofproducing a local high electric field.

FIGURES 16A and 16B show still further methods of launching shock waves.

FIGURE 17 illustrates another arrangement for controlling the launchingof shock waves.

FIGURE 18 is a schematic diagram illustrating the pick off of a voltageacross part of the semiconductor body.

FIGURES 19A through 19F are symbolic representations for a number ofapplications involving combinations of means for launching shock wavesand means for extracting information therefrom.

Microwave oscillator There have existed a number of basic techniques forthe generation and amplification of microwaves. Conventional devicesthat are useful for producing frequencies in the microwave range are,for example, the travelling wave tube and its variant, the backward waveoscillator, as well as the magnetron oscillator, the reflex klystron andothers. However, such devices have been pushed to their practicablelimits, due to their well known bulkiness, fragility, etc., in obtainingoperation at extremely high frequencies above 100 megacycles.

Another conventional device for microwave generation is the transistoroscillator. However, this device is limited to the production of verysmall output powers at moderately high frequencies. Anothersemiconductor device is one which exploits the so called nostronoscillations within a semiconductor body and which exhibits a negativeresistance region in its current-voltage characteristic. However, thenostron oscillator is necessarily limited to extremely small dimensionson the order of microns.

Negative resistance effects have also been exploited in other devicessuch as the tunnel diode and avalanche injection diode to provide highfrequency oscillations.

The aforesaid conventional transistor oscillator, the nostron oscillatorand other negative resistance oscillators that have been proposedheretofore are extremely dependent on the external circuitry in the formof resonant circuits for proper operation.

Another device for generating microwaves which has achieved prominencein recent years is the maser, the term standing for microwaveamplification by stimulated emission of radiation. The maser is a devicewhich relies on atomic and molecular processes within substances,generally when in the gaseous or solid state. Some limitations, however,are imposed upon the useful frequencies of operation for masers due tothe fact that complicated and bulky arrangements must be provided forpumping these devices and, further, the pump frequency must usually beof higher frequency than the generated frequency.

The microwave oscillator of the present invention shares with certain ofthe maser devices the capability of providing substantial microwaveoutput power from the solid state.

The instant microwave oscillator device differs sharply from all theforegoing devices discussed above in that it relies primarily on anaturally occurring phenomenon which produces oscillations virtuallyindependently of external circuitry and whose principle of operation isbelieved to depend on the interactions in semiconductor crystals betweenphonons and charge carriers, i.e., holes or electrons, under theinfluence of extremely high electric fields. Phonons, as that term isunderstood in the art, refers to quanta of the lattice vibrations in acrystal.

When an electric field is applied to a homogeneous semiconductorspecimen which is in thermal equilibrium, this equilibrium is lost, and,in the most general case, the interactions between the field of thecarriers and the scattering mechanisms become very complex. In theordinary theory of carrier mobility, a drastic simplification is made byassuming that, while the carriers may have directed drift velocitysuperimposed upon their random thermal motions, their total energyremains unchanged by the application of the field. However, thisassumption is strict- 1y justified only for vanishingly small values ofthe field. and, for finite values, the electron temperature exceeds thatof the lattice. Thus, because the scattering is in general dependent onthe carrier temperature, it follows that a change in mobility will beobserved when the carrier temperature has been raised by the field.Thus, there are high field effects in which a departure from Ohms lawresults from a change in carrier mobility while the carrier densityremains constant. Further, another type of departure occurs when thefield becomes so high that additional carrier pairs are generated by theionization of lattice bonds.

For a full development of the theory of mobility changes which occur ina high electric field, reference may be made to an article in Progressin Semiconductors. edited by A. F. Gibson, Heywood and Co., Ltd.,London, 1957, at p. 213, and reference may also be made, as indicated inthat article, to the various theories propounded by Landau and Kompanejez, by Guth and Mayerhofer, by Seitz and Shockley, etc. For recentreports on experiments that have been conducted involving electric fieldeffects and associated hot electron phenomena and plasma formation,reference may be had to:

(1) The Oscillistor-Ne'-.v Type of Semiconductor Oscillator, Journal ofApplied Physcis, vol. 31, No. 9, September 1960, by R. D. Larrabee andM. C. Steele.

(2) Observations of Electron-Hole Current Pinching in Indium Antimonideby M. Glicksman and R. A. Powlus, Physical Review, vol. 121, No. 6, Mar.15, 1961.

(3) The Sogican-New Type of Semiconductor Oscillator by M. Kikuchi andY. Abe, Journal of the Physical Society of Japan, vol. 17, 1962, pp.881882.

(4) Hot Electrons in Indium Antimonide by M. Glicksman and W. A.Hicinbothem, Jr., Physical Review, vol. 129, No. 4, Feb. 15, 1963.

More pertinent to the basic phenomenon underlying the present inventionis believed to be the prior art knowledge with regard to the cooperativeinteractions of a traveling wave nature between coherent waves oflattice vibrations in solid materials and a stream of free chargecarriers moving through these materials. In most cases of interactionsbetween lattice vibrations and charge carriers which have beenconsidered previously by workers in the art, the lattice modes have beenacoustical in nature and the potential with which the carriers interacthas arisen either from changes in the energy gap, from the relativedisplacement of conduction band minima, or from piezoelectricpolarization resulting from certain transverse modes of vibration inpolar lattices lacking a center of inversion. For a detailed descriptionof several of these cases, reference may be had to:

(1) G. Weinreich, Physical Review, 104, 321, 1956.

(2) G. Weinreich, T. M. Sanders and H. G. White, Physical Review, 114,33, 1959.

(3) A. R. Hutson and D. L. White, Journal of Applied Physics, 33, 40,1962.

The description hereinafter will make particular reference to onesemiconductor material, namely GaAs, with which numerous experimentshave been performed following the discovery of the basic underlyingphenomenon of the present invention. It will be understood, however, bythose skilled in the art that other semiconductor materials,particularly polar semiconductors, may also be utilized in accordancewith the principles of the present invention.

Referring now to FIGURE 1, there is depicted a graph illustrating therelationship between the current through a semiconductor sample and theintensity of electric field E applied across this sample. It will benoted that the graph shows a substantially linear relationship betweencurrent I and average electric field E up to a threshold value ofelectric field E Thereafter, a discontinuity appears and it is beyondthis point that the oscillatory phenomenon according to the presentincention is operative. For values of E greater than E the currentfluctuates in C9 time even while E remains constant. The maximum valueof the current does not usually exceed the steady values which it has atE whereas the minimum value may be substantially less than the value atE This time variation of current is symbolized by the shaded region inFIGURE 1. For example, if the electric field is applied by means of ashort voltage pulse corresponding to an amplitude equal to or less thanE the current will have the time variation shown in FIGURE 2A; if theamplitude exceeds E the variation of current will be that shownschematically in FIGURE 23, high frequency fluctuations beingsuperimposed on the basic pulse shape.

It will be noted that in FIGURE 1, immediately after the threshold valueE is reached and operation commences in the shaded region, there isexhibited a sharp drop in conductivity. Thus, the discontinuity at Ecannot be associated with an increase in the number of charge carrierswithin the semiconductor sample, for example, an n-type GaAs disc orwafer. In operation, there is a predominance of only one type of chargecarrier. As is evident from FIGURE 1, the exhibited drop in conductivityis clearly indicative of the activity of substantially only one type ofcharge carrier within the wafer.

In FIGURE 3, which is a schematic illustration of one embodiment of thepresent invention, there is shown the basic device 1 which consistsessentially of a semiconductor wafer 2, typically of GaAs, as previouslyreferred to in connection with FIGURE 1. As is indicated in FIG- URE 3,this wafer has a thickness or length denoted by the symbol L which willbe referred to hereinafter. The semiconductor wafer 2 has contacts 3aand 3b alfixed thereto. These contacts comprise dots, typically of Sn,which are formed by alloying to the wafer 2. Shown connected to thewafer 2 is a source of power 4, for example, a constant voltage source,and suitable conductors attached to the contacts 3a and 311 for applyinga voltage to the wafer 2 thereby creating an electric field of suchpredetermined value within the wafer 2 as to produce the effectspreviously noted, that is, the sharp drop in conductivity and theconcommitant generation of microwave power. A load 5 is also shownconnected in the circuit and the output is derived therefrom.

For the sake of simplicity, FIGURE 3 is a schematic showing and, inactual operation, a convenient matching network would be interposedbetween the generator, that is, the active device 1, and the load 5.

In actual tests with GaAs samples, it has been found that in longsamples (approximately l mm.) the huetuations are random and consist ofvery intense noise with components up to 2000 megacycles/sec. In shortspecimeans (less than 2X10 cm. or 0.2 mm.) the fluctuations take theform of coherent oscillations, as depicted in FIGURE 2B, whose valuedepends on the length L of the sample in the direction of current flow,as illustrated in FIGURE 3.

The frequencies f, of oscillation are found to be given by theexpressions of f nv/L where, for a particular crystal of GaAs, where nis an integer and v is approximately equal to 10- cm./sec. which isapproximately equal to the drift velocity of the electrons at thethreshold value of field E where the oscillations first appear. Usuallythe frequency given by n=l is the only term, but strong harmonics up to12:5 have sometimes been found and occasionally the term n=l is entirelyabsent. These dimensional resonances have been observed under the rangeof v/L from 0.5 to 4.5 Gc/S (where Gc/S stands for gigaeycles or 10cycles/sec.) and, in a sample of irregular geometry, osciilations havebeen observed at f=6.5 Gc/S. Even in this last case, the oscillationsappear to build up within a few cycles so that extremely rapidmodulation is possible.

When the external circuit has negligible impedance, the depth ofmodulation of the same current may reach 30%. As stated previously, bythe use of a matching network, for example, a resonant cavity, thesample may be matched 6 to an external load. With such an arrangement,the overall efiiciency of conversion from D.C. to R.F. is 110%. The meanoutput power is limited by the thermal properties of deviceconstruction, but peak power of 4.5 Watts at about 1 Gc/S and 0.15 wattsat 3 Gc/S have been measured.

Having described the microwave oscillator embodiment of the presentinvention and the essential circuitry associated therewith, attention isnow turned to the techniques that may preferably be employed forpreparing the wafer, for making suitable contact to the semiconductorwafer, and for encapsulation of the entire device package.

The microwave oscillator embodiment as disclosed requires a structureconsisting typically of a piece of n-type GaAs with plane parallel endshaving ohmic contacts attached thereto. To provide this structure, thefollowing.

steps are followed. A piece of single crystal GaAs is lapped into a thinslice with a thickness or length, typically 40- microns or 0.4 mm, whichis slightly greater than the required sample length L, and discs 0.75mm. in diameter are cut from the slice with an ultrasonic tool. Afteretch ing for a predetermined time in an etch producing a smooth surfaceon n-type GaAs (e.g., white etch; sulphuric-peroxide etch), the discsare then ready for the next step.

Since ohmic contacts are desired, an n+ layer must be formed on thefaces of the discs. In the present process, alloyed contacts are madeusing pure tin which is a donor in GaAs. Spheres of tin 0.75 mm. indiameter are prepared for use by heating them to a very high temperature(-ll00 C.) on a graphite strip heater in an atmosphere of forming gas,holding a few minutes, and allowing them to cool. By using a heater withmany dimples, a number of spheres may be treated at once. This treatmentis necessary to improve the wetting of the GaAs by the molten tin in thelater stages of the process.

As shown in FIGURE 4, alloying is carried out in the alloying jig 6.Immediately before loading, the GaAs disc 7 and all parts of the jig 6are washed in 5% NaCN solution, rinsed in distilled water which has beenkept out of contact with glass, and dried under vacuum. The assembledjig is then pre'fired in purified forming gas. These precautions arenecessary in order to prevent the diffusion of traces of copper from theenvironment into the GaAs. In the absence of these precautions, the GaAsdisc 7 would be converted to p-type during alloying and rendereduseiess.

The jig 6 of FIGURE 4 has the following features. The cavity in whichailoying is carried out has a bore of 0.77 nun, just large enough topermit a tin sphere 8a to be inserted, followed by the GaAs disc 7, anda second tin sphere Sb. The clearance between the bore and the edge ofthe disc is too small to permit molten tin (which has a large angle ofcontact with GaAs) to penetrate and wet the sides of the disc. The blockof graphite in which the cavity is bored is split to permit easy removalof the finished device, the two halves being located by hollow stainlesssteel dowels, not shown. A second horizontal bore at one endaccommodates a Pt-Pt-Rh thermocouple, not shown, whose tip lies close tothe alloying cavity. I-Ieat for alloying is supplied by passing A.C.through the block of graphite. The whole system is enclosed in a glasscover, not shown, through which flows carefully purified and driedforming gas.

Because of the large angle of contact between molten tin and GaAs, theliquid metal will not spread to cover the whole of the faces or ends ofthe disc 7 and will not wet even a fraction of their area unless thetemperature is raised to the point where a large amount of GaAs isdissolved. Under these circumstances, an undesirable biconcave form isgiven to the remaining GaAs. To overcome this difiiculty, the alloyingprocess is carried out under carefully controlled pressure, rather afterthe fashion of diecasting. A closely fitting graphite plunger 9 isinserted in the mould cavity when it is loaded, above the upper ends,and is weighted by an additional ring of graphite which is hung over itsupper end. The upper end of the plunger fits into a depression orannular groove on the inner surface of the ring which hangs freely andsurrounds the main block of graphite. The weight of the ring is chosenso as to force the molten tin spheres 8a and 8b into intimate contactwith the plane faces of the GaAs without forcing the molten tin into theclearance between the circumference of the GaAs and the cylindrical boreor between plunger 9 and cylindrical bore. A weight of 0.3-0.5 gm. hasbeen found satisfactory.

The heating cycle is controlled by passing a fixed A.C. which wouldbring the alloying jig 6 to equilibrium at a temperature higher thanthat desired for alloying. The output from the thermocouple is fed to apotentiometric recorder, not shown, fitted with a limit switch whichturns off the current when the desired temperature is reached (SOD-550C.).

By means of this system, GaAs oscillators can be produced havinginterfaces between semiconductor and contacts which are parallel withinmicrons or less.

Referring now to FIGURES SA-SF, the several steps involved in theencapsulation of the device of the present invention are illustrated.After alloying, the initial structure consists of a disc 7 of GaAs,which is typically 25 microns thick and 0.75 mm. in diameter, sandwichedbetween the solidified Sn contacts 8a and Sb.

It is required (a) to be able to reduce the cross section of the activeGaAs portion in a geometrically regular manner and (b) to be able tomake very low inductance contacts to the external circuitry. These twoobjectives are met by the following system. The structure, as shown inFIGURE 5A, is first ground and polished with three plane faces parallelto the longitudinal axis so that the resultant transverse cross sectionis triangular and the overall shape of the structure is prismatic, asshown in FIGURE 5B. The structure of FIGURE 53 is then laid, as shown inFIGURE SC, in the approximate center of a cylindrical mould of TEFLON orsimilar material, approximately /2" in diameter, and an epoxy resin 11is run into a depth of approximately 3 When the resin is hardened, theentire assembly of the device structure surrounded by resin is removedfrom the mould and the lower portion of the assembly is ground away upto the line 12 as shown in FIGURE 5D.

The foregoing procedure thus enables the reduction of the cross sectionin a very simple manner and permits convenient handling of the device. 7The block of resin containing the device is now mounted beneath adrilling jig, not shown. This jig consists of a hardened and groundsteel plate containing three holes, two of which serve to guide asubsequent drilling operation. The third hole is covered by a small thinglass disc with an etched graticule on it which serves to define thedirection and exact center of the line joining the other two holes.Under a microscope the device is aligned manually with the adjacentgraticule and then clamped to the jig. The holes 12a and 121) aredrilled into the .hardened epoxy resin block 11 using the holes in thejig as guide bushings. These holes 12a and 121) are related in anexactly known way to the device, as shown in FIG- URE 5F.

Electrical connection to the sample can now be made using one of avariety of holders. These holders vary in electrical details but aresimilar mechanically. As shown in FIGURE 5E, two steel pins 13a and 13bare fitted into holes, drilled with the jig mentioned above, into aninsulating block 14. The pins 13a and 13b enter freely into holes 12a nd12b, respectively, in epoxy 'block 11 holding the sample. Two thinstrips a and 15b of phosphor bronze are fitted into the block 14 withtheir free ends on either side of the center line between the pins 13::and 13b. The strips 15a and 1515 project above the surface of the block14 and nearly parallel to the block and the free ends are tapered toabout .005". By means of the drilling jig which can be slipped onto thepins, the ends of the strips 15a and 15b can be arranged to coincidewith the Sn portions 8a and 8b. Thus, when fitted in place, strips, 15aand 1511 make electrical connection to the Sn portions 8a and 8b, eventhough they may be very narrow, while avoiding damage to the exposedsurface of the GaAs disc 7.

Because of their short length and very close proximity to the groundedblock 14, the inductance of the strips 15a and 15b can be made extremelylow. The inductance of the packaged oscillator is essentially zero, andno expensive package is required, all oscillators fitting a same packageeven though their dimensions vary greatly. Finally, the cross section ofthe GaAs disc 7 is readily adjusted at any time by lapping the exposedsurface.

Having described the first basic device embodiment of the presentinvention and the technique employed in its packaging and itsencapsulation, it is considered Well to summarize and restate in anotherway observations that have been made by examining the relationshipbetween current and voltage at the terminals of the device. Thesuperscripts given refer to explanatory statements hereinafter setforth.

When a potential V is applied between the ends of a bar of GaAs or InPof length L, the current at first rises linearly as voltage is increasedfrom zero. When the threshold voltage V is reached, however, the currentbegins to fiuctuate At first, current decreases to some value 1 which isless than the steady current value I corresponding to V This decrease isfollowed by a rise in current to a value I which is usually equal tosteady current value I and then by further fluctuations between 1 and IIf the voltage is now raised above V the current continues to fluctuate,the value of I usually remaining almost unchanged. In the case of longspecimens (L greater than 0.2 mm), the fluctuation is almost completelyrandom, resembling white noise with a bandwidth of the order or" 10cycles/ sec. Short specimens (L less than 0.2 mm.) behave similarly whenthe impedance of the external circuit is high, but generate coherentoscillations of current when the impedance is low The period of theseoscillations is found to be equal to the transit time of the electrons,calculated from the threshold current I The oscillations normally buildup to full amplitude within one cycle, have frequencies in the range 5 Xl0 6.5 X10 cycles/ sec, and values of I /I of 0.7*0.8.

In GaAs, the threshold electric field varies with L, from the value 1250V/cm. at L=0.5 cm. to 3700 V/cm. at L=2 10' cm. In InP, the values arevery scattered, but threshold fields of 6000 V/cm. are typical. In bothmaterials, the magnitude of the threshold field and, in GaAs, the natureof the instability, are unaffected by the nature of the contacts, thesurface condition of the specimen, irradiation by light, or theapplication of a magnetic field.

For further information in expansion of the above summary, reference maybe had to the IBM Journal of Research and Development, April 1964, p.141.

Electrical shock wave phenomenon and its application It has now beenfound that the previously observed fluctuations of current areassociated with a moving distribution of electric field and hence, ofpotential within a crystal specimen.

Observation methods and results thereof Referring now to FIGURE 6, thechanging potential distribution V (x, y, 1) over the plane surface of atypical specimen of GaAs was explored 'by a technique employing acapacitative probe 20 as illustrated therein. The separation of theprobe 20 from the GaAs specimen 21 was kept small and constant, but itsposition along the GaAs specimen could be changed by a micrometer stage.The signal from the probe was led to a sampling oscilloscope (not shown)having a certain impulse response 5 (1) and an input resistance R. Ifthe dimensions of the 9 rectangular probe face in the x and y directions(that is, parallel and perpendicular, respectively, to the current fiowin the GaAs specimen) are bx, y and its capacitance to the GaAs is C,the signal S displayed at the oscilloscope is:

CR m y+ yl2 x+ xl2 I b I I I I I y JL Ji y/ X 5XI2 g(t O l (a: y t)d:2:d, dt

For the apparatus used, 5x=15 microns, 5y=270 microns, and g(t) was apeak less than l0- sec. in width. Thus, the signal S represents anapproximation to the quantity CR[8V(X, y, t) /Bt] measured withresolutions of microns, 270 microns and 10* second, respectively.

A normal sampling oscilloscope presentation of S as a function of time tis very difiicult to interpret, and alternative forms of display wereemployed. In the first type, the probe position was held fixed; thesignal S was integrated electronically, and then displayed on anoscilloscope. The display given by the oscilloscope thus represented thetime variation of the quantity f S(r') dz o: V(x, y, t) with x and yconstant. In the second type of display, the instant of sampling t washeld fixed while x was varied over the length of the specimen. Thesignal S was displayed on an oscilloscope whose horizontal defiectionwas proportional to x. This display gave a picture of 6V(x, y, t)'Ot asa function of x, the distance along the specimen, with y and t heldfixed.

Measurements were made of a specimen of n-type GaAs of length L=2l0microns and cross sections 3.5 X 10- cm. Its resistance at low fieldswas 16 Ohms.

ectangular positive pulses of a few nanoseconds duration were applied bya circuit with an impedance of ohms so that approximatelyconstantcurrent conditions were achieved, rather than the constantvoltage conditions in the microwave oscillator embodiment. Instabilitiesof current occurred at specimen voltages above 59 volts.

FIGURE 7A shows several wave forms V(t), with the applied voltage justless than the threshold value of 59 volts, measured at equal intervalsof x. It is apparent that, under these circumstances, the time variationof potential at a point it merely reproduces that at x=L multiplied bythe fraction x/L, as would be expected for a homogeneous conductor. Ifthe initial voltage exceeds the aforesaid voltage, however, verydifferent results are obtained as illustrated in FIGURE 7B. \Vhen theinstability begins at about the middle of the pulse, the potential atx=L rises sharply, remains high until almost the end of the pulse andthen drops rapidly again. At other points in the specimen, thisvariation is not reproduced. A roughly equal rise in potential of aboutvolts occurs simultaneously at all points, but the drop takes placeearlier at small values of x. At a given value of x, the values of Vbefore the rise and after the fall are approximately equal.

Referring now to FIGURE 8, it will be appreciated that additionalinformation is obtainable from a display of BV/Zit as a function of xwith t as a parameter. The circumstances were the same as depicted inFIGURE 78 except that the amplitude of the applied current was slightlygreater so that the instability occurred at the beginning of the pulse.In the trace indicated 1, at the top of the FIGURE 8, the variation of8V/6t is approximately linear with x, showing that the electric field isbuilding up uniformly in the specimen. In trace 2, obtained after adelay of 6.6 l0* secs, this linear distribution is beginning to undergoa distortion. By trace 11, this distortion has taken the form of awell-defined negative maximum of BV/Et, extending over about 30 microns;elsewhere in the crystal, 8V/Bt=0. From this instant, this negativemaximum propogates in the x direction (which is also the direction ofelectron fiow) with unchanged shape until, at about trace 34, it reachesthe anode. From here on, the display becomes somewhat confused becauseof random differences between successive pulses, but it can be seen thatthe events of traces 2-11 are reproduced, at least in a general way, intraces 35-44. Inspection will show that the velocity with which themaximum travels is constant and equal to about 8X10 cm./ sec. This valueis about equal to that estimated from data on other specimens for thedrift velocity of electrons at the threshold. The average electric fieldwithin the disturbance may be estimated roughly from the observed widthand potential drop. The value found is about 2x10 V./ cm.

The data of both FIGURES 7 and 8 can be represented by a time-dependentpotential distribution shown diagrammatically in FIGURE 9A. A fixedcurrent is forced through the specimen of such a value that thethreshold for instability is just exceeded. At the instant after thecurrent is turned on, a linear distribution of potential exists (curve1). Thereafter, the instability gives rise to a narrow region of veryhigh local electric field (slope of potential distribution), whichbuilds up new the cathode (curve 2). As time passes, the high fieldregion propagates along the specimen while the local field elsewhereremains approximately constant (curves 3, 4 and 5). Finally, thehigh-field region reaches the anode at x:L and passes out of thespecimen. At some fixed interme diate point of observation x thepotential rises from V to V when the highfield region builds up, remainsat V while the high-field region is to the left of x and then dropsrapidly back to V as the region passes x Clearly, the drop will occurlater at larger values of x (cf. FIGURE 7B). The time derivative ofpotential is, of course, zero except within the high-field region asshown in FIGURE 8.

As it appears from FIGURE 8, once built up, the disturbance propagateswith constant velocity and unchanged shape. Accordingly, suchdisturbance might be described as a shock wave which quickly reaches anequilibrium form. Consequently, the function V(x, t) for the Shock wavecan be written in the form V(x-ct) where c is its velocity. Thus, theoperations 8/6t and c a/ax are equivalent, and traces such as 11-34 inFIGURE 8 can also be interpreted as graphs of the electric fielddistribution EU).

When a constant voltage (low impedance) source is used to drive thespecimen, as in the microwave oscillator case, the situation is somewhatdifferent from that just discussed. The potential is now fixed at thepoint x=L, as well as at xzO, and the growth of a high-field shock wavecauses the field in parts of the specimen outside the wave to bereduced. The effect is illustrated in FIGURE 9B. In particular forcurves 3, 4 and 5, the field at the cathode becomes less than the valuecorresponding to curve I which was sufiicient to launch the shock wave.Thus, since the achievement of a critical local field E is the eventwhich triggers the instability, the existence of one shock wave withinthe specimen can inhibit the launching of a second wave from the cathodeby reducing the field there to a value below E This inhibition, is, ofcourse, removed when the first shock wave reaches the anode and thepotential distribution reverts temporarily to curve 1. By contrast, thefield at the cathode under constant-current conditions is independent ofthe presence or absence of a shock wave elsewhere in the specimen andfurther shock waves can be launched at any time.

The following is a discussion of the results summarized previously.

(a) The onset of current fluctuations corresponds with the appearance ofshock waves.

(b) As soon as the shock wave appears, the field in other parts of thespecimen is reduced below E Since GaAs is a nearly ohmic conductor underthese field conditions, the current is reduced in proportion.

(c) A new shock wave is launched when, for any rea- I 1 son, theconduction current rises to I and the field at the cathode consequentlyreaches E (d) The constancy of I with changes of applied voltage can beexplained in the same way.

(e) The effectiveness of the inhibition process illustrated in FIGURE 9Bis obviously greatest in short specimens. In long specimens, the changesin field at the cathode are too small to control the launching of latershock waves which is thought to occur at random times.

(f) The same remarks apply to short specimens operating under nearlyconstant-current conditions.

(g) Under constant-voltage conditions, the inhibition mechanism isstrong enough in short specimens to ensure that a shock wave is launchedfrom the cathode when, and only when, the preceding wave reaches theanode. The generation of new shock waves thus takes place in a periodicmanner.

Some evidence of this effect can be seen in FIGURE 8 where a new Waveappears to be launched at a variable time around traces 35 44. Thisfigure was obtained under conditions of high but not infinite externalimpedance so that the inhibition effect was Weak but not non-existent.

(h) The period of the oscillations must be equal to the transit time ofthe shock wave which, as we have seen, travels with about the velocityof the electrons at threshold.

(i) The first shock wave builds up to its full amplitude before leavingthe cathode. The modulation of the current is then as great as it canever be.

(j) In very short specimens, the voltage LE may be less than the voltageacross the freely propagating shock wave. In that case, the shock waveprobably remains attached to the cathode until some higher voltage isapplied. Thus, the apparent threshold voltage will be higher than LEThis effect might account for the observed curvature of the LVcharacteristics of very short specimens.

(k) Since the shock wave travels in the same direction as the electrons,it cannot involve minority carriers.

(1) In InP, the hole lifetime appears to be long enough that holeinjection is possible from an avalanche associated with a very highfield at the anode. This high field apparently arises only on thearrival there of the shock wave. Thus, the current must decrease for atime equal to the transit time of the shock wave before it can increaseas a result of avalanche injection.

Device applications The application and utilization of the uniquephenomenon that has been discovered, namely, the moving distribution ofelectric field that can be produced within a crystalline specimen, willnow be considered in more detail. However, before going into thespecific detailed device embodiments, it is well to state first thebasic considerations leading to device implementation as a result of theobservations that have been made.

I. M'ethods of controlling the launching of shock waves The fact hasbeen noted in connection with the curves of FIGURE 8 that, once builtup, the shock wave can propagate apparently in equilibrium form eventhough the applied field is reduced below threshold. This fact is borneout by reference to FIGURES 10A and 10B wherein are shown several pulseshapes. The first pulse shape in FIGURE 10A is a voltage pulse that isapplied, in a circuit substantially the same as shown in FIGURE 3, tothe crystalline wafer which is connected to a typical load. However, inthis particular instance, the power source 4 would comprise, as oneexample and for convenience only, a pulse generator developing a basicpulse A as shown in FIGURE 10A and superimposed thereon a spike B. Thespike B is of such magnitude that the total voltage exceeds, fora briefinterval, the threshold value V also shown in FIGURE 10A.

The resultant current pulse through the circuit of FIG- URE 3 has theform shown in FIGURE 108. Thus, it will be seen that the current dropsfrom its maximum value at that instant of time when the total voltageexceeds the threshold V but the current remains down after the spike Bhas terminated. In a typical case, the spike B would have a totalduration of 0.2 nanosecond but the current decrease would continue for aperiod of about 2 nanoseconds (which for the particular specimen isapproximately equal to the transit time of the shock wave).

It will therefore be appreciated that a shock wave will continue topropagate under conditions where it cannot be initiated. The shock wavewill continue to propagate even though the impulse that caused it tobegin propagating has terminated. Thus, even though the applied fieldhas dropped below threshold when the voltage spike B has ended, thecurrent decrease, as illustrated in FIGURE 10B, continues for a longerperiod of time.

The aforedescribed operation is that of a one-shot pulse stretchingcircuit with energy gain. Its more specific applications would be as aline driver, memory driver, or as a logical circuit using simultaneouslyor sequentially applied input signals.

In the last named application, that is, as a logical circuit,

the same result of current variation as depicted in FIG- URE 10B wouldbe realized by applying several input signals in the form of voltagespikes to the device. In an inclusive 0R logical circuit, each voltagespike would be selected to be of sufi'icient magnitude to cause thetotal voltage to exceed the threshold value V as indicated in FIGURE10A. Alternatively, an AND logical circuit would be simply realized bythe selection of relatively smaller voltage spikes whose applicationseparately would be insufficient but whose coincidence would have theeffect of causing the total voltage to exceed the threshold value VT;

A second basic method of launching shock waves for various specificdevice applications involves the imposition of local high fieldsapplied, for example, by means of a third electrode afiixed to thedevice wafer. This contrasts with the aforedescribed arrangementinvolving the application of over-voltage spikes to a two terminaldevice.

Referring now to FIGURES 11A, 11B, and 11C, there are shown severalschemes for the imposition of local high fields at various points on thedevice body 30 to produce the launching of the aforesaid shock waves. InFIGURE 11A, the normal anode and cathode contacts 31 and 32 are made toopposite ends of the body 30 but an additional electrode 33, denominateda trigger electrode, has been aifixed to the body, for example, byalloying to the bottom surface thereof. A basic power pulse is appliedto the terminal marked +DC and the cathode 32 is grounded, as shown inFIGURE 11A. The basic power pulse shape is shown in FIGURE 12A anddenoted V the threshold value again being shown by the symbol V Now,however, as contrasted With the previously described two terminaloperation, a voltage spike V is applied to the input terminal and thenceto the trigger electrode 33, as shown in FIGURE 11A. The trigger pulseshape is shown in FIGURE 123. The resultant current pulse is denoted Iin FIGURE 12C and, as was the case previously, the current drops on theapplication of the trigger pulse V but remains at the lower value for atime period greater than the duration of the trigger pulse V FIGURES 11Band 11C merely illustrate other possible coupling configurations. InFIGURE 11B, the third or trigger electrode is shown aflixed to the sameend surface as the cathode contact 32 and, in FIGURE 11C, the triggerpulse is capacitively coupled to the wafer.

Another specific device embodiment that is a variant of the deviceconfiguration as shown in FIGURE 11A is an embodiment where thepreviously described microwave oscillator mechanism is employed, that isto say, the power source is a constant voltage source and is applied, aswas shown in FIGURE 11A, to the anode 31. The same basic pulse shape isused as in-the previous example and is redepicted in FIGURE 13A.However, now the trigger pulse V is made greater than the transit timefor propagation of the shock wave throughout the body 3%). The result isthat the current takes the shape of the pulse shown in FIGURE 13C(labeled I What is hereby realized is a modulated oscillator whose timeperiod of generating oscillations is controlled by the duration of thetrigger pulse V and is, therefore, susceptible to very rapid modulation.

Referring now to FIGURE 14, the detailed physical structure of thedevice, previously shown schematically in FIGURE 11B, is herewithdepicted. The wafer 49 of GaAs, having a contact of AuGe, is shownmounted to a header 4-1 to which it is soldered. A thin wire or ribbon42 is soldered to the top surface of the wafer 40 to which an ohmiccontact 43 of AuGe has been made. The wire 42 is further connected toterminal posts 44 and 45. Also connected to these terminal posts arewires 46 and 47, respectively, and an additional wire 43 is connected tothe header 41, all three of these Wires being used for circuitconnecting purposes. A saw cut 49 divides the top contact 43 into twoportions, and the contact portion on the left forms the trig erelectrode and the other portion serves as the cathode. It is importantto keep the cathode area greater than about 80 percent of the maximumcrosssectional area of the wafer.

Other specific methods may also be employed to cause a local high field,as heretofore described, thereby to control the launching of shockwaves. Such another method would be, for example, to transfer groundconnections so as to pass current through a constricted region, asillustrated in FIGURE 15A. In the alternative, one can simply pulse sucha current as illustrated in FIGURE 158.

Still other methods of launching shock waves, for example, from a placeother than the cathode, are as illustrated in FIGURES 16A and 1613.FIGURE 16A shows the general two-terminal configuration previouslydescribed. However, in this embodiment, a slot 59 is placed in thesemiconductor body in order to constrict the area and to promote thedevelopment of a high local field in the region around the slot. Ofcourse, this method is very similar to that described above inconnection with FIGURES 15A and 153 except that here the embodiment isof a two-terminal device. Alternatively, to the same end, a portion ofrelatively high resistivity p may be included in the semiconductor bodyof lower resisting p as depicted in FIGURE 168, such that the development of the required high field will be promoted in the higherresistivity portion of the body. It will thus be seen that the effectivelength L of the body for propagation of the electrical shock waves hasbeen materially reduced in the above two cases.

Another arrangement, as illustrated in FIGURE 17, provides contact 51and 52 comprising the anode and cathode on one surface of thesemiconductor body and by use of a slot 53 the active region of thedevice is confined to the bulk portion immediately adjacent the slot 53.Thus, the total active length has been substantially reduced wherebytailoring of the device to fit specific electrical requirements may bereadily obtained.

11. Methods 0 locally extracting energy or information from shock wavesThe methods of locally extracting energy are roughly similar to the foreoing methods that have been described for launching shock waves.

For example, as illustrated in FIGURE 18, a voltage is picked oil acrosspart of the semiconductor body using ohmic contacts. As shown, anelectrode 60 is used for output purposes. Between this electrode 60 andanode contact 61, a voltage signal will appear only when the shock waveis present in the region between the contacts 69 and 61. Thus, theduration of this output voltage signal is equal to the transit time ofthe shock wave between contacts 80 and 61 and may be made much less 111.Combinations of launching and extracting means Up to now, variousspecific launching and extracting means have been described. What willnow be considered are combinations of these various means such thatdevices may be constructed to fulfill various electrical requirements.Referring now to FIGURES 19A-19F, these are symbolic representations fora number of applications involving the aforesaid combinations of meansfor launching shock waves in a semiconductor body and means forextracting information from that body. The symbols used in all theFIGURES are explained next to FIGURE 19C.

In the first case of a pulse stretching amplifier, as generallyexemplified by FIGURE 19A and which has been specifically exemplifiedpreviously in FIGURE 113, the output may be taken across the entire bodyor across a typical load which is connected to the appropriate pair ofoutput terminals.

The basic device of the present invention may also be used for delayline purposes and this is illustrated in FIGURE 19B where the symbol atthe input represents any of the launching means previously described andthe symbol at the output represents the local signal extracting meansalready described. As a delay line, arbitrarily long delays are possiblebecause of the self-sharpening nature of the shock wave. Even though theinput pulse may be degraded and of poor characteristics, the outputpulse, because it is generated by a shock wave phenomenon, will have asize and shape which are independent of the input pulse, provided onlythat the amplitude of that pulse is sulficient to launch a shock wave.

In FIGURE 19C, there is illustrated another typical application of alogical OR or NOR device wherein a number of separate inputs, heredenoted input 1 and input 2, embodying particular launching means, areapplied to the semiconductor body and an output is derived which isresponsive to the presence of a signal at either input 1 or input 2(logical OR). The logical NOR function can similarly be realizeddepending on the grounding point of the launching means.

In FIGURE 19D, a switch is illustrated for utilizing the electricalshock wave phenomenon of the present invention. In this example, theterm switch is used in the railroad sense. Which branch is taken in theembodiment of FIGURE 19D depends on which branch carries the mostcurrent at the instant when the shock wave arrives at the fork. This iscontrolled by pulsing the currents in the branches differentially or byusing additional contacts, shown dotted in the FIGURE, near the fork toobtain the same effect.

FIGURE 19E illustrates a shock wave combiner Where the individual shockwaves launched by the separate inputs A and B can propagate into thecommon output but there is good isolation between the separate inputs.

FIGURE 19F illustrates an inhibiting type of logic device. Thisembodiment is in accord with the previously expressed ideas on theoscillator mechanism, that is, the presence of one shock wave in thesemiconductor body working under constant voltage conditions inhibitsthe launching of further shock waves until the one shock wave reachesthe anode. By means of a suitable technique, for example, strobing, thelogical functions shown next to FIGURE 16F are obtained. Thus, it willbe seen that 15 the input signals A and B are applied at times I and 1and the outputs are sensed at times and t t and 2 t and t are chosen tosatisfy the following relationship:

where T is the transit time. Looking at the output portion of the pulsediagram at the sensed instant of time 1 an output signal will appearonly when input signal B is present. However, at a latter instant oftime 1 the precise function A and not B (A B) is obtained. An outputsignal is present at time 1 for example, in the first situation at thetop, when input signal A is present and input signal B is not present;in the third situation, even though input signal A, is present there isno output since input signal B is also present. Thus, the presence ofinput signal B inhibits the appearance of an output signal even thoughinput signal A is present.

in an alternative arrangement, an input signal B may be applied atanother point on the body (shown dotted) nearer to the output means thanis input signal A. By suitably proportioning the respective transittimes for the shock waves generated by input signals A and B, the sameessential inhibiting logical function may be obtained.

What has been described herein is an invention based on a discovery ofthe phenomenon of electrical shock waves which are produced byapplication of voltage beyond a threshold point to a crystalline bodyand, in particular, to a semiconductor crystalline body. Such phenomenonhas been illustrated as finding application in a variety of deviceembodiments. However, no attempt has been made to exhaust all of thepossible device embodiments that may be practicable. The notableadvantages that accrue to the exploitation of this unique electricalshock wave phenomenon will be appreciated by those skilled in the art,particularly the fact that the speed of operation is not dependent onthe achievement of very small physical dimensions.

Although the device geometries described have been mainly limited torectangular ones, it will be understood that neither constant crosssection nor plane external surfaces are necessary to the operation ofmany of the devices. For example, a body in the form of a truncatedpyramid or cone with contacts on the bases thereof may be used to obtaincontrol over the distribution of electric field.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. A signal translating apparatus comprising a body including a regionof semiconductive material of single conductivity type and whereincurrent is flowing in a given direction,

said region including means responsive to electric fields in excess of athreshold intensity applied along said given direction for varyingcarrier mobility to reduce the conductivity of said region such thatcurrent flow along said region is decreased,

means for applying electric fields at least of said threshold intensityin said region along said given direction, and

load means including resonant means coupled to said semiconductive body.

2. An apparatus for producing microwave oscillations comprising ann-type gallium arsenide wafer having a length less than 2X l cm.,

ohmic contact means connected to said gallium arsenide wafer,

means connected to said ohmic contact means for applying electric fieldsgreater than 2000 v./cm. in said gallium arsenide wafer to producecoherent sustained 16 current oscillations of microwave frequencytherein, and

load means connected to said gallium arsenide water.

3. An apparatus for producing microwave oscillations comprising ann-type indium phosphide wafer having a length less than 2X10 cm.,

ohmic contact means connected to said indium phosphide wafer,

means connected to said ohmic contact means for applying electric fieldsgreater than 6000 v./cm. in said indium phosphide Wafer to producecoherent sustained current oscillations of a microwave frequencytherein, and

load means connected to said indium phosphide wafer.

4. A signal translating apparatus comprising a body of semiconductormaterial of single-type conductivity capable of forming therein highelectric field regions which propagate along said semiconductive body,said semiconductive body exhibiting a first critical voltage at whichhigh electric field regions are formed.

said semiconductive body exhibiting a second critical voltage less thansaid first critical voltage at which high electric field regions whenformed are sustained and ropagated along said semiconductive body, and

means including voltage means and a load connected to saidsemiconductive body for causing said first and second critical voltagesto be applied in turn to said semiconductive body such that highelectric field regions are formed and propagated along saidsemiconductive body.

5. A signal translating apparatus comprising a semiconductive region ofsingle conductivity-type material.

said region having the innate property of being responsive to electricfields in excess of a threshold intensity to produce a high electricfield effect and cause a redistribution of electric fields within saidregion due to variations in carrier mobility so as to decrease theconductivity of said region,

means for supporting current flow along said semiconductive region in agiven direction and for applying electric fields in said semiconductiveregion along said given direction and at least in excess of saidthreshold intensity to produce said high electric field effect, and

load means coupled to said semiconductive region.

6. A signal translating apparatus as defined in claim 5 wherein saidsemiconductive region is of non-uniform cross section and includes aconstricted portion along said given direction, said applying meansbeing operative to apply electric fields at least in excess of saidthreshold intensity at least in said constricted portion.

7. A signal translating apparatus as defined in claim 5 wherein saidapplying means includes a plurality of electric field-applying means,each of said plurality of electric field-applying means beingindependently operative to increase electric fields in excess of saidthreshold intensity in said semiconductive region.

8. A signal translating apparatus as defined in claim 5 wherein saidapplying means further includes biasing means for applying electricfields less than said threshold intensity to said semiconductive regionalong said given direction, said biasing means and each of saidplurality of electric field applying means being cooperative to increaseelectric fields in excess of said threshold intensity in saidsemiconductive region.

9. A signal translating apparatus as defined in claim 5 wherein saidapplying means includes a plurality of electric field-applying means,two or more of said plurality of electric field-applying means beingconcurrently operative to increase electric fields in excess of saidthreshold intensity in said semiconductive region.

10. A signal translating apparatus as defined in claim 5 wherein saidapplying means includes a plurality of elec tric field-applying means,said plurality of electric field 17 applying means being concurrentlyoperative to increase electric fields in excess of said thresholdintensity in said semiconductive region.

11. A signal translating apparatus as defined in claim wherein saidsemiconductive region includes a higher resistivity portion along saidgiven direction, said applying means being operative to appl electricfields at least in excess of said threshold intensity at least in saidhigher resistivity portion.

12. A signal translating apparatus comprising a semiccnductive region ofsingle conductivity-type material,

said material in bulk form having the innate property of beingresponsive to a constant voltage across said region of said material inexcess of a threshold value to periodically vary in time theconductivity of said semiconductive region such that current flow alongsaid semiconductivc region in a given direction fiuctuates periodicallyin the form of coherent sustained oscillations,

means for supporting current fioW along said semiconductive region in agiven direction and for applying a voltage at least in excess of saidthreshold value across said semiconductive region in said givendirection to periodically vary in time the conductivity of saidsemiconductive region, and

load means coupled to said semiconductive region.

13. A solid state device as defined in claim 12 wherein saidscrniconductive region is formed of n-type gallium arsenide.

A solid state device as defined in claim 12, wherein said semiconductivere ion is formed of n-type indium translating apparatus as defined inclaim d semiconductive region is formed of an nductivity material. A sinal translatin apparatus as defined in claim 12 wherein saidscrniconductive region is formed of an n-type material selected from thegroup consisting of gallium arsenide and indium phosphide.

17. A signal translating apparatus comprising a semiconductive region ofsingle conductivity-type material,

said material in bulk form having the innate property of beingresponsive to a constant voltage across said region of said material inexcess of a threshold value to produce time-varying electric fieldeffects which periodically vary in time the conductivity of saidsemiconductive region such that current fiow through said semiconductiveregion in a given direction fluctuates periodically in the form ofcoherent sustained oscillations, means for supporting current fiow alongsaid semiconductive region in a given direction and for applying avoltage at least in excess of said threshold value across saidsemiconductive region in said given direction to produce coherentsustained oscillations in load means coupled to said semiconductiveregion for receiving said coherent sustained oscillations.

A signal translating apparatus as defined in claim 'urther comprisingresonant means forming said load A solid state device as defined inclaim 17 wherein scrniconductive body is formed of a polar semiconmotivematerial.

A signal translating apparatus comprising a body of semiconcluctivematerial of single conductivity-type,

said semiconductive body itself including first means responsive toelectric fields in excess of a threshold intensity for redistributingelectric fields in said semiconductive body to define low and highintens ty regions so as to decrease the conductivity of saidsemiconductive body such that current fiow through said scmiconductivebody is decreased, means for supporting current flow along saidsemiconductive body in a given direction and for applying electricfields in said semiconductive body and along said given direction atleast in excess of said threshold intensity to redistribute electricfields in said semiconductive body and to define a high electric fieldregion in at least one portion of said semiconductive body, and loadmeans coupled to said semiconductive body. 21. A signal translatingapparatus as defined in claim 2%) further including ohmic contacts tosaid semiconductive body, said applying means being connected to saidohmic contacts.

22. A signal translating apparatus as defined in claim 2% wherein saidfirst means responsive to said electric fields is located in one portionof said semiconductive body.

23. A signal translating apparatus as defined in claim 20 wherein saidsupporting and applying means are connected along one surface of saidsemiconductive body.

24. A signal translating apparatus as defined in claim 2% wherein saidsemi-conductive body itself further includes second means responsive toelectric fields of a given intensity and less than said thresholdintensity for propagating a high electric field region after said highelectric field region has been produced in said semiconductive body fromsaid one portion, said supporting and applyi g means being operative toapply electric fields at least in excess of said given intensity inother portions of said semiconductive body.

25'. A signal translating apparatus as defined in claim 2 lwherein saidfirst and said second operative means are alternately to cyclicallyproduce and propagate high electric field regions through saidsemiconductive body to periodically vary in time the conductivity ofsaid semiconductive body such that current flow through saidsemiconductive body fluctuates periodically in the form of coherentsustained oscillations.

26. A signal translating apparatus as defined in claim 2% wherein saidsecond means is operative to propagate said high electric field regionsalong said semiconductive body at least at a velocity of approximately10 cm./sec. 27. A signal translating apparatus as defined in claim 24wherein said load means comprises means capacitively coupled to saidsemiconductor body for sensing changes in electric field intensitytherealong.

28. A signal translating apparatus as defined in claim 24 wherein saidload means is connected across a section of said semiconductive bodyalong which said high electric field region is propagated.

A signal translating apparatus comprising a body of semiconductivematerial of single conductivity-type material wherein current is flowingin a given direction,

said semiconductive body including in a portion thereof first meansresponsive to electric fields in excess of a threshold intensity toproduce an electrical shock Wave,

said semiconductive body including second means responsive to electricfields of a given intensity less than said threshold intensity topropagate an electrical shock Wave after said electrical shock wave hasbeen produced along said semiconductive body, the presence of saidelectrical shock Wave in said semiconductive body varying theconductivity thereof to decrease current flow through saidsemiconductive body,

means for applying electric fields in said semiconductive bod along saidgiven direction to produce and propagate an electrical shock wave alongsaid semi' conductive body in said given direction, and

load means coupled to said scmiconductive body.

3%. A signal translating apparatus as defined in claim 29 wherein saidapplying means includes first electric field-applying rueans forapplying electric fields of said given intensity in said semiconductivebody and second electric field-applying means cooperative with saidfirst 19 electric field-applying means for increasing electric fieldsapplied in said semiconductive body in excess of said thresholdintensity.

31. A signal translating apparatus as defined in claim 29 wherein saidapplying means is operative to apply electric fields in excess of saidthreshold intensity at least in said portion of said semiconductive bodywhereat said first means is located.

32. A signal translating device comprising a body including asemiconductive region of sin le conductivitytype and through whichcurrent is flowing in a given direction,

means for applying electric fields in excess of a threshold intensity tosaid semiconductive region along said given direction,

said semiconductive region including means responsive to electric fieldsin excess of said threshold intensity for producing and supporting atime-varying electric field gradient, the presence of said electricfield gradient in said semiconductive region varying the conductivity ofsaid semiconductive region such that current flow in said semiconductiveregion is decreased, and

load means coupled to said semiconductive region.

33. A signal translating apparatus as defined in claim 32 wherein saidproducing and supporting means is operative to propagate saidtime-varying electric field gradient along said semiconductive region ata velocity approximately equal to the drift velocity of charge carriersin said semiconductive region.

34. A signal translating apparatus as defined in claim 32 wherein saidproducing and supporting means is operative to propagate saidtime-varying electric field gradient along said semiconductive region ata velocity at least approximately equal to cm./se

35. A signal translating apparatus comprising a body including a portionof semiconductive material of single conductivity-type material,

means for supporting current flow along said semiconductive portion in agiven direction and for applying electric fields in said given directionand at least in excess of a threshold intensity in said semiconductiveportion,

said semiconductive portion having the inherent property of beingresponsive to electric fields of said threshold intensity for producingcyclically and for propagating successively high electric field regionsalong said semiconductive portion for a distance L and at a velocity v,the presence of a high electric field region along said semiconductiveportion varying the conductivity of said semiconductive portion suchthat current fluctuations therethrough take the form of coherentsustained oscillations having a frequency given by the relationship v/L,and

load means coupled to said semiconductive body.

36. A signal translating apparatus as defined in claim 35 wherein saidvelocity v is at least approximately equal to 10 cm./sec.

37. A signal translating apparatus as defined in claim 35 wherein saidsupporting and applying means includes a constant voltage source, andfurther comprising ohmic contact means connecting said constant voltagesource to said semiconductive region.

38. An oscillator device comprising a semiconductive body of uniformconductivity type,

means connected to said semiconductive body for supporting current flowalong said semiconductive body and for applying electric fields to saidsemiconductive body along a given direction,

said semiconductive body itself including means responsive to saidconnected means for producing and propagating in cyclic and successivefashion high electric field regions in said given direction along saidsemiconductive body at a velocity v, said semiconductive body exhibitingdifferent conductivitic during the presence and absence, respectively,of a high electric field region such that current flow through saidsemiconductive body varies periodically in the form of coherentsustained oscillations having a frequency related to said velocity v,and

load means coupled to said semiconductive body.

39. An oscillator device as defined in claim 38 wherein said producingand propagating means is operative to propagate said high electric fieldregions along said semiconductive body at least at a velocity ofapproximately 10 cm./sec.

40. A signal translating device comprising a semiconductive body ofsingle conductivity-type material,

means connected to said semiconductive body for applying electric fieldsin said semiconductive body at least of a given intensity and forsupporting current flow along said semiconductive body in a samedirection,

said semiconductive body having the innate property of being responsivesolely to electric fields or a threshold intensity to produce a highelectric field region and to electric fields of a given intensity topropagate a high electric field region along said semiconductive body,the appearance of a high electric field region along said semiconductivebody being effective to reduce the conductivity and modulate currentflow through said semiconductive body, said connected means beingoperative to apply electric fields in excess of said given intensityduring the presence of a high electric field region along semiconductivebody,

input means for momentarily increasing the intensity of electric fieldsapplied in at least a portion of said semiconductive body in excess ofsaid threshold in tensity, and

load means coupled to said semiconductive bod 41. A signal translatingdevice as defined in claim 4-6 wherein said input means is connected atan intermediate portion of said semiconductive body.

42. A signal translating device as defined in claim "at; wherein atleast said input means is capacitively coupled to said semiconductivebody.

43. A signal translating device comprising a semiconductive body ofsingle conductivity-type,

means for supporting current flow along said semicon' ductive body andfor applying electric fields of given intensity in said semiconductivebody along a given direction,

said semiconductive body itself including first means in one portionthereof responsive to electric fields of a threshold intensity forgenerating a high electric field region wherein the mobility of chargecarriers is changed,

first and second means independently operative in time sequence toincrease the intensity of electric fields in said semiconductive body atleast in excess of said threshold intensity,

said semiconductive body itself further including second meansresponsive to said supporting and applying means for propagating a highelectric field region along said semiconductive body at a fixedvelocity, the presence of a high electric field region in saidsemiconductive body varying the conductivity so as to modulate currentflow through said semiconductive body in said given direction andinhibit said first means, and

load means coupled to said semiconductive body and operative at timeintervals subsequent to said first and second input means for sensingthe presence of a high electric field region along said semiconductivebody whereby logical functions are achieved.

44. A signal translating device comprising a body of semiconductivematerial of single conductivity-type and wherein current is flowing in agiven direction,

means for applying electric fields less than and in excess 2i of acritical intensity in said semiconductive body along said givendirection,

said semiconductive body including means for producing a substantiallyuniform electric field distribution along said given direction inresponse to applied electric fields less than said critical intensityand an electric field gradient along said given direction in response toapplied electric fields in excess of said critical intensity,

the presence of an electric field gradient varying the conductivity ofsaid semiconductive body to decrease current fiow therethrough, and

load means coupled to said semiconductive body.

45. A signal translating device as defined in claim 44 further includingohmic means formed of a semiconductive material of said singleconductivity-type for connecting said applying means to said body ofsemiconductive material.

46. A signal translating device as defined in claim 44 wherein saidsemiconductive body includes means for producing said electric fieldgradient in a portion thereof, said semiconductive body furtherincluding means responsive to said applying means for propagating saidelectric field gradient thus produced along said semiconductive body insaid given direction.

47. A signal translating device comprising a body of semiconductivematerial of single conductivity-type and wherein current is flowing in agiven direction,

means for applying electric fields in excess of a threshold intensity insaid semiconductive body along said given direction,

said semiconductive body including means responsive to said electricfields in excess of said threshold intensity for producing atime-varying high electric field efiect due to a change in carriermobility within said semiconductive body to periodically vary theconductivity of said semiconductive body and modulate current fiowtherethrough, and

load means coupled to said semiconductive body.

48. A signal translating device as defined in claim 47 wherein saidproducing means is localized in a portion of said semiconductive body.

49. A signal translating device as defined in claim 48 wherein saidsemiconductive body includes means for propagating said high electricfield effect along said semiconductive body and wherein said load meansis responsive to said current flow in said semiconductive body.

51'). A signal translating device comprising a body of semiconductivematerial,

means for supporting current fiow along said semiconductive body and forapplying electric fields in excess of a threshold intensity in saidsemiconductive body along a same direction,

said semiconductive body having the innate property of being responsiveto said last-mentioned means when electric fields in excess of saidthreshold intensity are applied therein for producing, supporting, andpropagating a time varying electric field effect due to variations incarrier mobility within said semiconductive body to vary theconductivity of said seciconductive body and modulate current fiow insaid same direction, and

load means coupled to said semiconductive body.

51. A solid state device for generating coherent oscillations comprisinga semiconductive body having a length less than 2 x lO crn.,

said semiconductive body having the innate property of being responsiveto a constant voltage applied thereacross in excess of a threshold valveto periodically vary in time the conductivity of said semiconductivebody such that current fiow through said semiconductive body fluctuatesperiodically to produce coherent sustained oscillations,

means for supporting current flow in said semiconductive body and forapplying a voltage in excess of said threshold value across saidsemiconductive body to produce said coherent sustained oscillations, andload means coupled to said semiconductive body. 52. A solid state deviceas defined in claim 51 wherein said semiconductive body has a lengthgreater than 1 micron and less than 2 10 cm.

53. A solid state device as defined in claim 51 wherein saidsemiconductive body is formed of an n-type material selected from thegroup consisting of gallium arsenide and indium phosphide.

54. A solid state device as defined in claim 51 wherein saidsemiconductive body is formed of n-type gallium arsenide and having alength of 0.5 cm., and said applying means is operative to applyelectric fields having an intensity of at least 1250 v,/cm. in saidsemiconductive body.

55. A solid state device as defined in claim 51 wherein saidsemiconductive body is formed of n-type gallium arsenide and saidapplying means is operative to apply electric fields having an intensitygreater than 2000 v./cm. in said semiconductive body.

56. A solid state device as defined in claim 51 wherein saidsemiconductive body is formed of n-type indium phosphide and saidapplying means is operative to apply electric fields having an intensitytypically in the order of 6000 v./cm. in said semiconductive body.

57. A solid state device as defined in claim 51 further including ohmiccontacts to said semiconductive body and means for serially connectingsaid applyin means and said load means to said ohmic contacts.

58. A solid state device as defined in claim 51 wherein said ohmiccontacts are formed of semiconductive material defining a non-rectifyingjunction with said semiconductive body.

59. A solid state device as defined in claim 51 wherein saidsemiconductive body is formed of a III-V semiconductor compound.

60. A solid state device comprising a body of semiconductive material ofsingle conductivity-type and having a common section and a plurality ofbranch sections,

said semiconductive material having the innate property of beingresponsive to electric fields of a threshold intensity for producing ahigh electric field region and to electric fields of a given intensityless than said threshold intensity for propagating said high electricfield region after said high electric field region has been produced inthe direction of applied electric fields, the presence of said highelectric field region varying the conductivity of said semiconductivematerial, and means for supporting current fiow along and for applyingelectric fields in said common section and a selected one of said branchsections to produce and propagate a high electric field region alongsaid common section and said selected one of said branch sections. 61. Asolid state device comprising a body of semiconductive material ofsingle conductivity-type and having a common section and a plurality ofbranch sections,

said semiconductive body itself including first means responsive toelectric fields in excess of a threshold intensity for producing anelectrical shock wave,

said semiconductive body itself further including second meansresponsive to electric fields of a given intensity less than saidthreshold intensity for propagating said electrical shock wave aftersaid electrical shock Wave has been produced along said semiconductivebody in the direction of said electric fields of said given intensity,the presence of said electrical shock wave varying the conductivity ofsaid semiconductive material,

first means for supporting current flow along and for applying electricfields of said given intensity in said common section and each of saidbranch sections of said semiconductive body, and

1. A SIGNAL TRANSLATING APPARATUS COMPRISING A BODY INCLUDING A REGIONOF SEMICONDUCTIVE MATERIAL OF SINGLE CONDUCTIVITY TYPE AND WHEREINCURRENT IS FLOWING IN A GIVEN DIRECTION, SAID REGION INCLUDING MEANSRESPONSIVE TO ELECTRIC FIELDS IN EXCESS OF A THRESHOLD INTENSITY APPLIEDALONG SAID GIVEN DIRECTION FOR VARYING CARRIER MOBILITY TO REDUCE THECONDUCTIVITY OF SAID REGION SUCH THAT CURRENT FLOW ALONG SAID REGION ISDECREASED, MEANS FOR APPLYING ELECTRIC FIELDS AT LEAST OF SAID THRESHOLDINTENSITY IN SAID REGION ALONG SAID GIVEN DIRECTION, AND LOAD MEANSINCLUDING RESONANT MEANS COUPLED TO SAID SEMICONDUCTIVE BODY.